The fisherman shared the odd specimen with scientist, who then recorded the strange filing in a study that was published online Monday in the Journal of Fish Biology.

It’s not the first time a two-headed shark has ever been seen, but it’s very rare. Only six other instances have been published in a reputable journals. Michael Wagner, a study co-author and researcher at Michigan State University, told LiveScience.com it was the first time such a bizarre specimen has been found in a bull shark, making it extra peculiar.

The abnormality, scientifically called "axial bifurcation," happens when the embryo starts to split into twins, but the process is not completed, Wagner told OurAmazingPlanet.com. It's an infrequent deformity that transpires in other animals, human too.

"Halfway through the process of forming twins, the embryo stops dividing," he said.

The two-headed fetus probably wouldn’t have lasted long in the wild, Wagner said. "When you're a predator that needs to move fast to catch other fast-moving fish … that'd be nearly impossible with this mutation," he said.

Wagner added that recording the mutated shark in scientific journals could aid in discovering how these deformities occur in sharks and other animals.

In some cases, people are attracted to animals with two heads, such as snakes and turtles, Wagner said and added there’s even a small market for such bizarre creatures.

Specimens of some of the two-headed sharks that can be seen today date back to the late 1800s when deformed animals procured high prices, he said.

The two-headed shark also probably would have been doomed by its small body. "It had very developed heads, but a very stunted body," Wagner said.

The stunted body was a result of all the energy in the shark’s body being focused on the two heads instead of its core, he added.